Area Forecast Discussion
Issued by NWS Boise, ID

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FXUS65 KBOI 060359

Area Forecast Discussion
National Weather Service Boise ID
859 PM MST Mon Dec 5 2016

.DISCUSSION...Latest models solutions were similar to previous
runs with regard to snowfall timing and amounts through Tuesday.
Snow has not been reported in SE Oregon yet, although radar and
satellite trends indicate that the snow will start in Baker County
and northern Harney County between 9 pm and 11 pm MST. The snow is
expected to spread into the Treasure Valley (including the Boise
metro) between 3 am and 5 am. The light snow should continue
through the morning commute and end by late morning. Total
snowfall amounts of up to an inch are still expected in the
valleys, with 1-3 inches in the mountains. Temperatures are
already running a little colder than forecast minimums in some
locations (e.g. Twin Falls)...therefore will update overnight


.AVIATION...Deteriorating conditions through the night as snow
spreads over the area. Snow will bring MVFR and local IFR
conditions along with widespread mountain obscuration. As of 03Z
snow near KBKE and expected to move into KMYL around 05Z, KBNO
around 07Z, KEUL/KBOI around 12Z and KJER/KTWF around 18Z. Surface
winds generally variable 10 knots or less. Winds aloft westerly
15-25 knots up through 10K feet MSL.


SHORT TERM...Latest system coming in from the northwest a little
slower than previously forecast. System will bring light snow to
our CWA with up to one inch in the valleys and 1 to 3 inches in
the mountains. Duration will be 6 to 10 hours in northern areas
and 4 to 6 hours in the south. Latest timing begins snow in
eastern Oregon around midnight PST north to 2 AM PST south and
going through 9 AM-11 AM PST Tuesday. In Idaho, snow should begin
around 2 AM MST north and west, and 3 am MST to 7 AM MST south and
east, and continue through noon MST west to 2 PM MST east. This
timing puts snow on Treasure Valley roads during morning commuting
time and even a half inch of snow may cause problems. Clearing and
colder Tuesday night and Wednesday, especially with new snow on
the ground. Patchy fog in the northern valleys Wednesday morning.
Wednesday will be the coldest day so far this season with lows 5
below to 5 above zero in the mountains and zero to 15 above in the
valleys. Highs Wednesday only 15 to 25 in the mountains and 20 to
30 in the valleys. No significant winds.

LONG TERM...Wednesday night through Saturday...Wednesday night
will begin dry, mostly clear, and cold ahead of an incoming
Pacific system which will move in from the south and west and
spread snow across the region Thursday morning into Friday. Latest
model runs have brought in a mild Pacific air mass for Friday, so
will see temperatures warm 5-12 degrees between Thursday and
Friday`s max/min temperatures. Precipitation falling as snow
through Thursday to valleys floors will likely switch to a cold
rain by Friday afternoon below about 4500 ft msl as snow levels
rise. Cold air in the lowest elevations of the Snake Plain will
take a bit longer to scour out with the incoming system, so the
changeover to rain could take a little longer than other areas
with light accumulations of snow early Friday morning. Mountains
will continue to accumulate snow through the period. Friday`s
warmer temperatures are expected to hold through Saturday for
temps just above normal.

Saturday night through Monday...Unsettled through the extended
period with models showing a series of waves passing through.
Problems arise with timing and placement so confidence in the long
term is low at this time. Snow levels begin to drop early Sunday
leaving valley locations with some mixed precipitation. Snow
levels drop to valley floors Monday so any form of precipitation
for that day will be in the form of snow. By Tuesday temperatures
start to rise changing things to rain for elevations below 2500





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